Method of and apparatus for making solder connections



Feb. 24, 1942. w INGERSQN 2,274,413

METHOD OF AND APPARATUS FOR MAKING SOLDER CONNECTIONS Filed Jan. 4, 1941FIG.

l/Vl/EN 70/? W. E. lNGE RS ON A T TORNEV jii'atented Feb. 24, 1942ltIETHOD OF AND APPARATUS FOR MAKING SOLDEB CONNECTIONS William E.Inger-son, New York, N. Y., asslgnor to Bell Telephone Laboratories,Incorporated, New York, N. Y., a corporation of New York ApplicationJanuary 4, 1941, Serial No. 373,104

' 4 Claims.

This invention relates to a method of and apparatus for solderconnecting lead wires to electrical units.

For the purpose of explanation and not in the sense of the invention tosuch use, the invention is described as being used in solder connectinga lead wire to a metal coated thermistor unit;

In the drawing.

Fig. 1 is a view in perspective of a cutter device for cutting a wire ofsolder, the wire being shown inserted in the cutter and the cutter havinbeen operated to cut off a piece of the wire;

Fig. 2 is a side elevational view partly in section of a mold with thelead wire and a piece of the solder wire inserted in a cavity in themold;

Fig. 3 is a view corresponding to Fig. 2, but with a flame applied tothe mold and with the solder in a molten condition about an end of thelead wire;

Fig. 4 is a side elevational view of a thermistor unit with the leadwire equipped with a button of solder resting on the electrode surfaceof the unit, a second mold resting on the button of solder and a heatedtool resting on the mold;

Fig. 5 shows the position of the members shown in Fig. 4 minus theheating tool and after sufficient heat has been applied to melt thebutton of solder: and.

Figs. 6 and 7 show, respectively. a top and a side view of thethermistor unit with the lead wires solder connected thereto.

The cutter I shown in Fig. 1 comprises a block 2 having an upwardlyextending end portion 3, the end portion being deeply slotted at 4 toreceive a knife 5 and apertured at 6 to receive a wire of solder I, theaperture extending entirely through the end portion 3 and beingintersected by the slot 4. A stop bar 8 is pivotally supported by ascrew 9 on the block 2 and is arranged for movement in line with one endof the aperture 6 to limit thrusting of the wire 1 through the block 2.The knife 5 comprises a blade portion Ill having a reenforcing bar H onits upper portion. The blade portion I0 is disposed within the slot 4and may be moved to sever the wire 1. The bar ll serves to stiffen theblade portion l0 and is made thicker than the width of the slot 4 and isso arranged that it will act as a stop to prevent driving of the lowersharpened edge of the blade portion l0 against the bottom of the slot 4.Predetermined length pieces of solder wire may be cut from the wire 1 bythrusting the or wire I through the aperture 6 and into engagement withthe stop bar 9 and then by forcing the knife 5 downwardly within theslot 4. Movement of the knife 5 may be accomplished by ap plying adownward pressure against the bar II. The piece of solder severed fromthe wire 1 comes out of the cutter l in the form of a solder pellet l2and is later used in forming a button of solder on the end of the leadwire.

The pellet l2 as shown in Fig. 2 is placed in a cavity IS in the moldI4. The mold l4 comprises a plate l5 made of material to which solderwill not adhere and through which heat may be transmitted to the pelletl2. A suitable material for the plate i5 is aluminum. One end It of theplate I5 is secured by means of the screws H to a suitable support l8.The free end I9 is offset from the plane of the end l6 and is providedwith the cavity H which is of suflicient area to receive an end portionof the lead wire 20 and all of the material in the pellet l2. The pelletI2 is placed in the cavity l3 and an end of the lead wire 20 is alsothrust into the cavity. Heat is then applied to the plate IE to melt thepellet 12. The heat may be applied as shown in Fig. 3 by means of theflame 2| from a burner 22. The pellet I2 is melted down into the cavityl3 and upon removal of the flame 2|, solidifies on the end of the leadwire 20 in the form of the cavity l3 which is of such contour that itwill mold the material in the pellet l2 into the form of a button 23.

The wire 20 with the button 23 of solder formed thereon is placed asshown in Fig. 4 on the thermistor unit 24 and so that the roundedportion of the button 23 is in contact with an electrode 25 provided onthe thermistor unit 24. The electrode 25 may be a suitable coating ofmetal formed on the thermistor 24. A second mold 26 is then employed totransmit heat to the parts and make a solder connection between the wire20 and the electrode 25.

The mold 26 comprises a plate 21 of heat transmitting material which hasno affinity for solder. A suitable material for the plate 21 isaluminum. The plate 21 is secured at one end by means of the screws 28to a movable support 29. A cavity 30 is provided in the lower surface ofthe plate 21 to receive the material in the button 23 when the button 23has been heated to the melting point of the solder material. The cavity30 is of general hemispherical form and has a channel 3| extendingtherefrom to the outer end of the plate 21 to accommodate a portion ofthe lead wire 20. Heating of the button 23 is accomplished by placing aheated tool 32 on the plate 27. The tool 32 may be a conventional typeof soldering iron. Heat from the tool 32 is transmitted to the button 23through the plate 27. When the button 23 becomes molten, the weight ofthe tool 32 plus the weight of the plate 27 causes the plate 2? to movedownwardly until the plate 2'5 comes to rest on the electrode 25, Fig.5. The material in the button 23 is pressed upward into the cavity 36and, upon removal of the tool 32 and cooling of the material makes asolder connection 33 between the wire Zll and the electrode 25. Thesolder connection 33 is shown in Figs. and 6. In Fig. '1 two lead wiresare shown connected to the electrodes of the thermistor unit 24.

What is claimed is:

1. A method of solder connecting a lead wire to a unit having a surfaceto which solder will adhere, comprising forming on an end of said wire asolder button having a rounded portion, placing said rounded portionagainst said surface, resting on said button a mold made of materialhaving no aflinity for solder and having an indentation therein adaptedto receive the amount of material in said button, resting a heated toolon said mold until the solder is melted sufliciently to adhere to saidsurface and take the form of the indentation in said mold and removingthe heated tool from said mold.

2. A method of solder connecting a lead wire to a surface to whichsolder will adhere, comprising making a pellet of solder, placing saidpellet and an end of said wire in a mold of material to which solderwill not adhere, heating said mold to melt said pellet and cooling saidmold to form a button of solder on the end of said wire, placing saidbutton on said surface. resting a second mold of material to whichsolder will not adhere, on said button, heating said second mold to meltsaid button, pressing said second mold down on said button while thematerial in said button is in a molten condition and allowing saidsecond mold and the solder contained therein to cool and form a solderconnection between said wire and said surface.

3. A method of solder connecting a lead wire to a surface to whichsolder will adhere, comprising cutting a piece of solder into pelletform, placing said pellet and an end of said wire in a cavity in analuminum plate, heating said plate to melt said pellet, allowing saidplate and the solder held in the cavity thereof to cool to form a buttonof solder on the end of said wire, placing said button on said surface,placing a mold plate of aluminum on said button, and so that a cavity insaid mold plate is in register with said button, resting a heated toolon said mold plate until said button is in a molten condition. and thematerial in said button has flowed up into said cavity, and thenallowing said mold plate and the solder in the cavity therein to cool toform a solder connection between said wire and said surface.

4. An apparatus for making a solder connection between a unit having asurface to which solder will adhere and a lead wire comprising incombination, a plate made of material having no aflinity for solder, anindentation formed in the upper surface of said plate to cast a drop ofsolder in button-like form on an end of said wire, means to heat saidplate, a second plate having no allinity for solder, an indentation inthe lower surface of said second plate adapted to receive said wire andthe amount of solder cast on said wire and a heated tool bearingdownwardly on said second plate to heat said second plate to the meltingtemperature of said solder, and press said solder against said unit andupwardly into the indentation in said second plate.

WILLIAM E. INGERSON.

